1. Field of the Invention
The present invention relates to a motor which takes out the rotational output from the central portion of a motor main body, and in particular to a motor that is preferably configured to the stop driving of an electromagnetic driving stop device.
2. Related Background Art
Conventionally, an electromagnetic driving motor was typically composed of a stator yoke, a coil, a rotor and others in a unit as one block, a rotor shaft protruding from its electromagnetic driving motor, wherein the output was transmitted by providing a rotational output member, for example, a gear, on the rotor shaft protruding therefrom, and using the rotation of its gear.
On the other hand, an electromagnetic driving motor having a stator yoke disposed radially to the rotational axis direction is well known in a stepping motor constituted by the electromagnetic driving motor, as described in Japanese Patent Application Laid-Open No. 3-207254.
In the conventional examples, however, in the former case, the rotor shaft protruding from an electromagnetic driving motor block is inboard within the electromagnetic driving motor, but a portion protruding from the electromagnetic driving motor block is in so-called cantilevered form. If a rotational force is transmitted to a working member having a load in this state, a radial force is applied on the gear of the rotor shaft, due to a reaction against that load, that is, a side pressure is applied on the rotor shaft, to flex the rotor shaft at its free end portion in cantilevered form. On the other hand, the rotor shaft has a force applied to restore the flexed state to counteract the load of the working member. That is, if the rotor shaft is rotated, the rotor shaft itself turns, whirling.
But there is a problem that, because an oscillation is transmitted to the gear as a transmission mechanism on the side of the working member, giving rise to a chatter sound or chatter oscillation and giving against the trend in recent years for silent motors, thereby producing, manufactured products degraded in quality. Also, this led to another problem that side pressure is applied on the rotor shaft, which causes a concentrated stress to be applied on the bearing, resulting in poor motor performance. On the other hand, there was a problem with products having an electromagnetic driving motor mounted so that when the rotor shaft can not be protruded from the aspect of the space, they can not cope with the current constitution of compact products.
Also, in the latter case (Japanese Patent Application Laid-Open No. 3-207254), when there was an obstacle in a radial space direction of the rotor (when there was another part in this radial space portion in mounting on the product), the use of an electromagnetic driving motor having a pencil-like rotor shaft protruding therefrom was obliged to cope with this, resulting in the previously described problem.